On Apr 15, 2009, at 8:55 AM, joseda wrote: > > That was the trick! I fixed by adding a new voltage source of -15V > (i called > Vee) > > But why is not -Vcc the same as Vcc multiplied by -1?
Vcc is only a name of a network. > Vcc is 15V V(Vcc) is 15V. Vcc is just a name. Now in *some* cases, ngspice will assume that you mean V(Vcc) when you enter Vcc. Not all SPICE dialects do this, and ngspice only does this is certain contexts. This is arguably a confusing misfeature. For one thing, it means it's a bad idea to use characters like "-" in ngspice netnames. > so -Vcc should be -15 V but it doesn't work this way!! To what voltage source is -Vcc connected to make it -15V? I see no such source in your circuit. > Anyway, thanks! > > > You have a node named "-Vcc". You haven't attached this node to > anything outside the opamp. Presumably you intended to attach a > negative power supply. The opamp model contains a current source > attached to this node, so letting it float makes rather high voltages. > > John Doty Noqsi Aerospace, Ltd. > http://www.noqsi.com/ > j...@noqsi.com > > > -- > View this message in context: http://www.nabble.com/problem-to- > simulate-an-astable-multivibrator-with-uA741-opamp- > tp23057811p23060560.html > Sent from the gEDA - User mailing list archive at Nabble.com. > > > > _______________________________________________ > geda-user mailing list > geda-user@moria.seul.org > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user > John Doty Noqsi Aerospace, Ltd. http://www.noqsi.com/ j...@noqsi.com _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user